If you're still having trouble, think of this. Without addons, your browser is capable of turning that code into something executable. So it can decode it on its own, basically. At the most basic level of thinking, you are looking for a way you can use your browser to give you the decoded script. So how can you input the encoded script into the browser and expect an output?

While the other ones took me around a minute each to complete... this one was quite the midnight brain teaser! I went from to to to and, after fifteen minutes of the W3School's "try-it-yourself" JavaScript render-er (I saw the hint in the code), I went

This site is great ^_^

Now I just have to figure out how to trick Sam's uber-leet anti-csrf referrer checker...